S-alkyl phosphorodihalogenidodithioate are known compounds which find utility as intermediates for the production of compounds which exhibit biocidal properties, particularly insecticidal and herbicidal properties.
A number of processes for the production of S-alkyl phosphorodichloridodithioate are known and some of them are reviewed in U.S. Pat. No. 3,879,500 and in greater detail in Methoden Der Organishen Chemie Band XII/2, Thiel 2 -- pages 682-683 and 739-740 (1963) published by Georg Thieme Verlug; Stuttgart Germany. The present process is believed to produce better yields in shorter times and at lower temperatures.
The reaction of alkyl mercaptans with phosphorous trichloride to yield S-alkyl phosphoro dichloridothioate is known. The reaction of phosphorodichloridothioate with elemental sulfur to yield S-alkyl phosophorodichloridodithioate is known. Finally, the reaction of S-alkyl phosphorochloridotrithioate with S,S-dialkyl phosphorothiotrichloride to yield S-alkyl phosphorodichloridodithioate is disclosed in U.S. Pat. No. 3,879,500. However, there is no teaching of a combination of these steps into a process which can produce S-alkyl phosphorodihalogenidodithioates in high yields of over 80% in short production times of under 8 hours.
It is therefore an object of the present invention to provide a method of producing high yields in short times of S-alkyl phosphorodihalogenidodithioates. It is a further object to provide such a method wherein the starting materials are readily available.
The most recent process for the production of S-alkyl phosphorodichloridodithioate, taught in U.S. Pat. No. 3,879,500, requires at least 13 hours to achieve net yields of less than 70%. These results are reported for S-methyl phosphorodichloridodithioate and the other results reported indicate much less satisfactory results are achieved with higher alkyl groups.